Engine speed indicator for a vehicle

ABSTRACT

The present invention relates to an engine speed indicator for a vehicle, which is driven by a combustion engine ( 4 ). The engine speed indicator comprises a first indicating means ( 1, 13 ) arranged to show the actual member of revolutions of the engine and second indicating means ( 7   a - b,    8   a,    14 ) arranged to show at which number of revolutions or within which range of number of revolutions a minimal emission of at least one emission gas is obtained from the vehicle during operation of the combustion engine ( 4 ). The engine speed indicator also comprises a third indicating means ( 8   a,    15  which is arranged to show an emission level of said emission gas at the actual value of the number of revolutions. A driver can hereby drive the vehicle in such a manner that the emissions of emission gases are substantially minimal.

BACKGROUND OF THE INVENTION AND PRIOR ART

[0001] The invention relates to an engine speed indicator for a vehicleaccording to the preamble of claim 1.

[0002] The emission of different emission gases from an engine variesprincipally with the engine speed but the emission quantity also varieswith other factors such as the delivered engine power. In Otto cycleengines, emission gases such as carbon dioxide, water, carbon monoxide,uncombusted hydrocarbons and nitrogen oxides are created during thecombustion. In diesel engines, also sulphur oxides and carbon particlesare created in addition to the above mentioned emission gases. Forenvironmental reasons, it is important that vehicles are driven such theemissions of such more or less unhealthy emission gases are reduced asfar as possible. The emission quantity of different emission gases of avehicle varies with the specific properties of the combustion engine butalso with the properties of the exhaust gas filter system. Therefore,the emission quantities of the emission gases may vary considerablybetween different vehicles. For. this reason, it is difficult for adriver to drive a vehicle such that the emission of the emission gasesis reduced substantially optimally.

[0003] U.S. Pat. No. 4,244,210, U.S. Pat. No. 4,523,457 and DE 19621896show engine speed indicators in vehicles, which comprise different kindsof indicating means, intended to indicate an engine speed at which aminimal fuel consumption is obtained. A number of emission gases arecreated in a quantity, which is substantially proportional to the fuelconsumption. For example, carbon dioxide is created in a quantity, whichis substantially proportional to the fuel consumption. Most emissiongases are created in a quantity, which is related to different operationconditions. For example, the creation of carbon monoxide and nitrogenoxides is promoted. when a local lack of oxygen is the case, thecreation of hydrocarbons when a high temperature and an oxygen surplusare the case and the creation of visible smoke (carbon particles) ofdiesel engines when the engine power is high and when the oxygen surplusis insufficient The emissions of these emission gases may be minimal atengine speeds, which considerably differ from the engine speed where thefuel consumption is minimal.

SUMMARY OF THE INVENTION

[0004] The object of the present invention is to provide an engine speedindicator having a design such it in an illustrative and simple mannerindicates to a driver of the vehicle recommended operation conditionwhere the emission of at least one emission gas is at a minimal level.Thereby, the driver has the possibility to drive the vehicle in a mannersuch that the emission of the emission gas is substantially minimal.

[0005] The above mentioned object is achieved by the initially mentionedengine speed indicator which is characterized by that which is mentionedin the characterizing part of claim 1. The quantity of the emission gas,which is created during the combustion process in a combustion engine,is principally related to the engine speed. Thereby, it is possible toindicate a number of revolutions or a range of number of revolutionswith a relatively high accuracy at which the emission of an emission gasis substantially minimal. Such a number of revolutions or range ofnumber of revolutions may be based on measures performed on the vehiclein question or on a vehicle with a corresponding type of engine and acorresponding exhaust gas filter system. Advantageously, the secondindicating means provides a clear indication of such number ofrevolutions or range of number of revolutions for several differentemission gases. Alternatively, a number of revolutions or a range orrevolutions may be indicated at which a total weighted minimal emissionof several emission gases is obtained. Such a number of revolutions orrange of number of revolutions may be weighted dependent of the dangerof the different emission gases. Consequently, in order to estimate theemission of different emission gases from a vehicle the ability of theexhaust gas filter system to eliminate different emission gases mustalso be taken into consideration. The second indicating means ought tohave such a design that the driver without losing his attention to thesurrounding traffic perceives the recommended engine speed at which thevehicle is driven with a minimal emission of emission gases.Consequently, the engine speed indicator indicates by said first andsecond means a difference between the actual engine speed and arecommended engine speed. With knowledge of said difference in enginespeed, the driver has the possibility to adjust the driving of thevehicle such that said difference is reduced. Preferably, the differenceis reduced in that the driver engages a new gear in the gearbox, whichgives an engine speed, which better corresponds the recommended numberof revolutions. Advantageously, also automatic gearboxes may becontrolled in a corresponding manner such that a gear change the wholetime is obtained which gives a minimal emission of emission gases.

[0006] According to a preferred embodiment of the present invention, theengine speed indicator comprises a third indicating means which isarranged to indicate an emission level of said emission gas at theactual number of revolutions. With a knowledge of the actual emissionlevel and the minimal emission level, the driver here obtains an ideaabout how much the emission of said emission gas may be reduced if thedriving of the vehicle is adjusted such that the recommended number ofrevolutions is achieved. Consequently, in the cases where only a smallreduction of the emission level of the emission gas is obtained, it isnot as important to change the vehicle as in the cases when a largerreduction is obtained.

[0007] According to a preferred embodiment of the present invention,said first indicating means comprises a movably arranged indicatingmember which is arranged to show the actual value of the engine speed.Many conventional engine speed indicators comprise a pivotally arrangedpointer the outer end which points on the actual value of the number ofrevolutions which is marked along a circular path. According to analternative, said second indicating means may comprise at least oneindicating member which is permanently arranged along said path, whichindicating member shows at which number of revolutions or within whichrange of number of revolutions a minimal emission of at least oneemission gas is obtained. For example, the indicating member maycomprise a suitably colored path with an extension along the range ofthe revolutions where a minimal emission of an emission gas is obtained.Advantageously, several such indicating members are arranged in order toindicate suitable ranges of number of revolutions for different emissiongases. A driver observes, with such permanent indicating members, in asimple manner if the vehicle is driven with an engine speed within therange of number of revolutions recommended by the indicating member.

[0008] According to another preferred embodiment of the presentinvention, said third indicating means comprises at least one lightgenerating member which through the generation of light of differentcolors indicates the emission level of said emission gas at the actualengine speed. For example, a green light may be emitted when theemission level is satisfactory, a yellow light, when it is notcompletely satisfactory, and a red light, when it is unacceptably high.Thereby, the driver obtains a simple and clear indication of theemission level of said emission gas. Advantageously, said lightgenerating member is a light emitting diode. A light emitting diode maycomprise a semiconductor material such that the light emitting diodeemits light with different colors when current flows through thesemiconductor material. For example, a light emitting diode comprisingthe semiconductor material gallium phosphide may emit red, green andyellow light.

[0009] According to another preferred embodiment of the presentinvention, a control unit is arranged to receive information concerningthe engine speed and the delivered engine power, after which the controlunit is arranged to activate the second indicating means such it showsat which number of revolutions or within which range of number ofrevolutions a minimal emission of said emission gas is obtained at theactual engine power. The delivered engine power may for example beestimated with knowledge of the fuel consumption. With knowledge of thefuel consumption of the engine, the delivered engine power may beestimated by means of stored measured values for the actual type ofengine. Alternatively, the engine power may be determined by measuringsuitable parameters. For example, this may be performed by means oftorque sensors, which measure the actual torque in a portion of thedrive train of the vehicle. With knowledge of the measured torque, theengine power may be determined. Since consideration here also is takento the actual delivered engine power, the range of number of revolutionsat which a minimal emission of said emission gas is obtained may bedetermined with a high accuracy. Preferably, the control unit is alsoarranged to initiate the activation of said third indication means inorder to indicate an emission level of said emission gas. The controlunit takes here into consideration both the engine speed and thedelivered engine power, which has as a result that the emission level ofsaid emission gas may be determined with a high accuracy.

[0010] According to another preferred embodiment of the presentinvention, the engine speed indicator comprises a display having animage surface and a first indicating means in the form of a pointer theposition of which on said image surface indicates the actual enginespeed and the delivered engine power. The driver may here in a simpleand visible manner, via the position of the pointer, be informed aboutthe actual engine speed and delivered engine power. Advantageously, saiddisplay comprises second means in the form of a graph which shows atwhich number of revolutions or within which range of number ofrevolutions a minimal emission level of said emission gas is obtained.The distance between the position of the pointer and the graphillustrates in a clear manner on the image surface how wrong the actualengine speed is in relation to the recommended. The extension of thegraph shows at which number of revolutions as a function of deliveredengine power a minimal emission of said emission gas is obtained. If thevehicle is driven in a manner such that the pointer has a position at arelatively large distance from the graph, this is a clear indication tothe driver that a new gear ought to be engaged in the gear box.Preferably, said display comprises third indicating means in the form ofat least a contour line which connects power ranges with a specificemission level of said emission gas. Preferably, several such contourlines are marked for different specific emission levels such that thedriver is informed with a relative large accuracy about the differencebetween the actual emission level shown by the pointer and the minimalemission level shown by the graph. The more contour lines that arelocated between the pointer and the graph shows how much the emission ofsaid emission gas may be reduced by the engagement of a more suitablegear.

SHORT DESCRIPTION OF THE DRAWINGS

[0011] In the following preferred embodiments of the invention are shownas examples with reference to the attached drawings, in which:

[0012]FIG. 1 shows an engine speed indicator according to a firstembodiment of the present invention,

[0013]FIG. 2 shows an engine speed indicator according to a secondembodiment of the present invention,

[0014]FIG. 3 shows an engine speed indicator according to a thirdembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0015]FIG. 1 shows an engine speed indicator having a conventional basicconstruction. The engine speed indicator comprises a pointer 1 having aninner end portion which is pivotally connected to a central pant of theengine speed indicator and an outer end portion which is movablyarranged along a circular path 2 in order to indicate the value of thenumber of revolutions. The circular path 2 comprises indications, whichindicate the value of the engine speed. A sensor 3 is arranged tomeasure the number of revolutions of a combustion engine 4. The sensor 3is, for example, a tachometer, which measures the number of revolutionsof a flywheel 5, which is fixedly connected to the crankshaft of theengine 4. The sensor 3 emits a signal, which corresponds to the value ofthe number of revolutions to a control unit 6. The control unit 6initiates a pivotal motion of the pointer 1 to a position, whichcorresponds to the number of revolutions measured by the sensor 3. Theengine speed indicator also comprises three indicating members 7 a-cprovided substantially in parallel, which have an extension along a partof the path 2. The indicating members 7 a-c symbolize three differentemission gases. The extension of the indicating members 7 a-c along thepath 2 shows the range of number of revolutions within which thecombustion engine 4 emits a minimal quantity of the respective emissiongases. For example, the indicating member 7 a indicates within whichrange of number of revolutions the quantity of emitted uncombustedhydrocarbons is minimal, the indicating member 7 b indicates withinwhich range of number of revolutions the quantity of emitted carbonmonoxide is minimal and the indicating member 7 c indicates within whichrange of number of revolutions the quantity of emitted nitrogen oxidesis minimal. Consequently, in this case it is suitable to drive thevehicle within an engine speed between 1200-1300 r/min in order tominimize the emission of the three above mentioned emission gases. Theemissions of the above-mentioned emissions gases vary with the specificproperties of the engine and also with the kind of exhaust gas filtersystem used. Corresponding indicating members 7 a-c in another vehiclemay therefore show other ranges of revolutions where a minimal emissionof said emission gases is obtained.

[0016]FIG. 2 shows an engine speed indicator provided with a pluralityof light emitting diodes 8 arranged in a row along said path 2. Eachlight emitting diode 8 symbolizes thereby a small range of number ofrevolutions. The light emitting diodes 8 comprise a semiconductormaterial such that they may emit three different colors namely, green,yellow and red. In a corresponding way as in the embodiment in FIG. 1, asensor 3 here measures the number of revolutions of the combustionengine 4. The sensor 3 emits a signal, which corresponds to the value ofthe number of revolutions to a control unit 6. The control unit 6initiates a pivotal motion of the pointer 1 to a position, whichcorresponds the number of revolutions, measured by the sensor 3. Thecontrol unit 6 here also obtains information from a fuel gauge 9, whichmeasures the supplied fuel quantity to the combustion engine 4. Withknowledge of the supplied fuel quantity and data stored in a memory unit10 concerning the specific properties of the engine 4, the control unit6 determines a value of the delivered power of the engine 4 for drivingof the vehicle. By means of stored data in the memory unit 10, thecontrol unit also determines within which range of number of revolutionsa minimal emission is obtained of an emission gas at the deliveredengine power. Since the emission quantity of an emission gas varies withthe engine power, a determination is here obtained of said range ofnumber of revolutions with an increased accuracy in relation to whenconsideration is taken only to the engine speed. The control unit 6initiates activation of the light emitting diode 8 a, which correspondsto the number of revolutions where a minimal emission is obtained. Thelight emitting diode 8 a emits here a green light. The control unit alsoinitiates activation of the light emitting diode 8 b, which correspondsto the actual number of revolutions. The light emitting diode 8 b emitshere a green light in case the emission level of the shown emission gassubstantially corresponds to the minimal emission level, a yellow lightwhen the emission level is not completely satisfactory and a red lightwhen the emission level is unacceptably high. The driver obtains here aclear indication by means of the color of the light emitting diode 8 bif a new gear ought to be engaged in order to decrease the emission ofthe emission gas. The engine speed indicator comprises a switch member11, which is settable in different positions in order to allow forswitching between different kinds of emission gases. If the switchmember 11 is set in a first position, the emissions quantity ofuncombusted hydrocarbons is shown, in a second position the emissionquantity of carbon dioxide and in a third position the emission quantityof nitrogen oxides.

[0017]FIG. 3 shows a display 12 having an image surface. The imagesurface comprises a vertical axis, which indicates delivered enginepower and a horizontal axis which indicates the engine speed. A pointer13 is arranged to take a position on the image surface, which informsthe driver about the actual engine speed and delivered engine power. Agraph 14 extends over the image surface. The graph 14 shows the enginespeed as a function of delivered engine power at which a minimalemission is obtained of an emission gas. A plurality of contour lines 15connect different power ranges with equal emission levels of saidemission gas. The contour lines 15 create closed loops along which asubstantially constant emission level of an emission gas is obtained.The contour line 15, which forms the innermost closed loop, contains apower range at which the lowest emission level of the emission gas isobtained. The contour lines 15, which extend around the innermost loop,show one for each loop increased emission level. In a corresponding wayas in the embodiments in the FIGS. 1 and 2, a sensor 3 measures thenumber of revolutions of a combustion engine 4. The sensor 3 emits asignal, which corresponds to the value of the number of revolutions to acontrol unit 6. The control unit 6 also receives information from a fuelgauge 9, which measures the quantity of fuel supplied to the combustionengine 4. With knowledge of the supplied fuel quantity and stored datain a memory unit 10 concerning the specific properties of the usedcombustion engine 4, the control unit 6 determines a value of the powerdelivered by the engine 4. The control unit 6 initiates a positioning ofa pointer 13 on the display 12, which informs the driver about theactual engine speed and delivered engine power. The engine speedindicator comprises also here a switch member 11, which is settable indifferent positions in order to allow for switching between differentkinds of emission gases. If the emission gas hydrocarbons is chosen tobe shown on the display 12, a graph 14 is shown where a minimal emissionof hydrocarbons is obtained. Furthermore, the contour lines 15 indicateon the display power ranges with equal emission levels of hydrocarbons.In order to obtain a minimal emission of an emission gas, a driver oughtto try to drive the vehicle such that the pointer 13 is as close to thegraph 14 as possible. In order to decrease the distance between thepointer 13 and the graph 14, in the example shown in FIG. 3, the driverpreferably engages a lower gear in the gear box such that the distancebetween the pointer 13 and the graph 14 decreases. However, in this caseit is not absolutely necessary to change gear since no contour line 15extends between the pointer 13 and the graph 14. The emission quantityof the emission gas may here only be reduced moderately by changing downthe vehicle.

[0018]FIG. 3 also schematically shows measurement equipment 16, which isarranged to measure the emission quantities of different emission gasesfrom the vehicle. The control unit 16 receives information concerningthe emitted quantity of said emission gases and stores these valuestogether with values concerning the engine speed and engine power. Ifdifferences exist between earlier stored values and measured values, thestored values in the memory unit 10 are corrected. Consequently, in thiscase the control unit 6 may use measured actual values for the specificvehicle.

[0019] The invention is not in any way restricted to the above-describedembodiments but may be varied freely within the scope of the claims.

1. An engine speed indicator for a vehicle driven by a combustion engine(4), wherein the engine speed indicator comprises a first indicatingmeans (1, 13) arranged to show the actual number of revolutions of theengine, characterized in that the engine speed indicator comprises asecond indicating means (7 a-b, 8 a, 14) arranged to show at whichnumber of revolutions or within which range of number of revolutions aminimal emission of at least one emission gas is obtained from a vehicleduring operation of the combustion engine (4).
 2. An engine speedindicator according to claim 1, characterized in that the engine speedindicator comprises a third indicating means (8 b, 15) arranged to showan emission level of said emission gas at the actual number ofrevolutions.
 3. An engine speed indicator according to any one of claims1 or 2, characterized in that said first indicating means comprises amoveably arranged indicating member (1) arranged to show the value ofthe actual number of revolutions along a graduated path (2).
 4. Anengine speed indicator according to claim 3, characterized in that saidsecond indicating means comprises an indicating member (7 a-c, 8 a),which is permanently arranged along said path (2), which indicatingmember (7 a-c, 8 a) shows at which number of revolutions or within whichrange of number of revolutions a minimal emission of said emission gasis obtained.
 5. An engine speed indicator according to any one of thepreceding claims 2-4, characterized in that said third indicating meanscomprises at least one light generating member (8), which indicates theemission level of said emission gas at the actual number of revolutionsby means of different colors.
 6. An engine speed indicator according toclaim 5, characterized in that said light generating member is a lightemitting diode (8).
 7. An engine speed indicator according to any one ofthe preceding claims, characterized in that a control unit (6) isarranged to receive information concerning the number of revolutions ofthe engine and the delivered engine power, after which the control unit(6) is arranged to activate the second indicating means (8 a, 14) suchthat it shows at which number of revolutions or within which range ofnumber of revolutions a minimal emission of said emission gas isobtained at the current engine power.
 8. An engine speed indicatoraccording to claim 7, characterized in that the engine speed indicatorcomprises a display (12) having an image surface and a first indicatingmeans in the form of a pointer (13) the position of which on said imagesurface indicates the actual number of revolutions of the engine anddelivered engine power.
 9. An engine speed indicator according to claim8, characterized in that said display (12) comprises second means in theform of a graph (14) which shows at which number of revolutions orwithin which range of number of revolutions as a function of thedelivered engine power a minimal emission level of said emission gas isobtained.
 10. An engine speed indicator according to claim 9,characterized in that said display (12) comprises third means in theform of at least one contour line (15), which connects power ranges witha specific emission level of said emission gas.